A hash table is a storage structure that calculates the storage address from a record key, k where f1(k) returns the storage address. Sometimes the hash function returns the same address for several keys (called collision). To fix this problem, a scheme called secondary hashing uses a sequence of independent hash functions f1, f2, etc. each which attempts to spread the key uniformly across the table. If f1(k) produces a collision, then f2(k) is tried and so forth. If a record insertion requires the services of hash function f1... fj to sucessfully find space for a new reocrd, it is said that we require j probes. Suppose the fraction a, (a < 1) of the table is filled when we make an attempt to store a new record. Let X be the random variable standing for the number of probes necessary to insert the new record.(adsbygoogle = window.adsbygoogle || []).push({});

What is the probability mass function of X. Find its mean and variance.

Does anyone here have a clue what values to use for X? And what the probability will be? I am clueless on what to do here. Any help would be great thanks.

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# Homework Help: Probability mass function of a hash table?

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